In mathematics, permutation relates to the act of arranging all the members of a set into some sequence or order, or if the set is already ordered, rearranging its elements, a process called permuting. Permutations occur, in more or less prominent ways, in almost every area of mathematics. They often arise when different orderings on certain finite sets are considered.
The combination is a way of selecting items from a collection, such that (unlike permutations) the order of selection does not matter. In smaller cases, it is possible to count the number of combinations. Combination refers to the combination of n things taken k at a time without repetition. To refer to combinations in which repetition is allowed, the terms k-selection or k-combination with repetition are often used. Permutation and Combination Class 11 is one of the important topics which helps in scoring well in Board Exams.
Permutation and Combination Formulas
There are many formulas involved in permutation and combination concept. The two key formulas are:
A permutation is the choice of r things from a set of n things without replacement and where the order matters.
nPr = (n!) / (n-r)!
A combination is the choice of r things from a set of n things without replacement and where order does not matter.